Overdose with Warfarin
Warfarin refers to indirect anticoagulants - substances that inhibit the coagulation link of hemostasis. Their reception prevents the formation of blood clots and stops the growth of already formed ones. This property of indirect coagulants has found active application in cardiology, neurology, and surgical practice. The anticoagulant effect of Warfarin appears after 2-3 days and fully develops by the end of the first week of administration. The drug is intended for long-term, often lifelong use in people with a tendency to thrombosis.
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The main indications are:
- acute or recurrent venous thrombosis;
- pulmonary embolism;
- transient disorders of cerebral circulation;
- ischemic stroke;
- prevention of recurrence of myocardial infarction and thromboembolic complications in the recovery period;
- prevention of thromboembolism in patients with cardiac arrhythmias;
- diseases of the heart valves or a condition after their prosthetics;
- prevention of postoperative thrombosis.
All diseases and conditions in which the risk of bleeding is increased are a direct contraindication to taking this drug. In particular, they include: diseases of the blood coagulation system, blood vessels, pregnancy, severe chronic damage to the liver and kidneys, gastric ulcer and duodenal ulcer, a history of hemorrhagic stroke.
A feature of taking Wafarin is the mandatory regular laboratory monitoring of the INR (International Normalized Ratio) throughout the therapy. INR is a laboratory test that reflects the state of the blood coagulation system, which is recommended by the World Health Organization. The optimal INR value while taking Warfarin is determined individually for a specific clinical situation and is usually in the range of 2-3.
With an incorrect dosing regimen or a violation of the dosage regimen, an overdose may develop, fraught with severe, including life-threatening complications.
How much warfarin is needed for an overdose?
The drug is taken once a day at the same time. The standard daily dose of Warfarin (on an outpatient basis) at the time of initiation of therapy is 2.5–7.5 mg. In the future, under INR control, the dose is adjusted until a stable therapeutic effect is achieved.
A dose of 20-30 mg / day is highly likely to cause symptoms of an overdose, although it is not entirely correct to talk about a specific amount of a substance in this case: in a number of patients, manifestations of an overdose develop when taking a standard maintenance dose, and some patients receive a shock without any complications dose. Individual sensitivity to the drug plays an important role in this case.
A possible overdose is monitored by the change in INR and characteristic clinical manifestations: if the indicator is more than 5, the dose is adjusted, more than 9 - the drug is canceled.
Signs of overdose
The main sign of an overdose with Warfarin is increased bleeding, manifested in the occurrence of bleeding, both explicit and latent. Patients taking the drug should pay attention to the appearance of certain signs that may clearly or indirectly indicate a complication that has developed.
Indirect signs of an overdose with Warfarin:
- bleeding gums when brushing teeth, eating solid foods;
- spontaneous nosebleeds;
- the appearance of small hematomas not associated with a previous injury;
- prolonged, not corresponding to the degree of damage, bleeding from wounds, even minor ones;
- in women, menstrual flow is more abundant and longer than usual.
Obvious signs of an overdose (require immediate medical attention):
- black tarry stools (melena) or vomit of "coffee grounds";
- urine staining - from pink to intense red;
- heavy bleeding from the nose or gums;
- in women - prolonged heavy menstruation, intermenstrual bleeding;
- cough streaked with blood in sputum;
- a sharp decrease in blood pressure, tachycardia, palpitations, shortness of breath;
- bleeding from small wounds and cuts lasting more than 10 minutes;
- dizziness, sharp headache, difficulty speaking, noise, ringing in the ears;
- visual impairment (double vision, flashing "flies" before the eyes, decreased acuity);
- a sharp cold snap of the limbs, numbness, a feeling of creeping on the skin, limitation of movements in the limbs;
- lack of coordination, unsteadiness of gait;
- sudden, intense pain in the abdomen or chest;
- extensive hematomas, areas of swelling that appear without connection with traumatic effects;
- massive edema of the lower extremities.
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First aid for overdose
When there are indirect signs of an overdose with Warfarin, it is necessary:
- Stop taking the drug.
- Contact your doctor to monitor INR and, if necessary, adjust the dose.
If there are obvious signs of bleeding, you must immediately call the ambulance team.
Antidote
A specific antidote that neutralizes the action of Warfarin is vitamin K and its synthetic analogue, Vikasol.
In the event of bleeding caused by an overdose of Warfarin, individually calculated doses of vitamin K (Vicasol) are prescribed until the activity of the coagulation unit is restored.
When is medical attention required?
Medical assistance is needed if:
- a pregnant woman, an elderly person, a child was injured;
- there are clear signs of external or internal bleeding;
- the state of health suddenly deteriorated sharply.
Depending on the severity of the condition, assistance is provided on the spot or hospitalization is made in the specialized department of the hospital, where the treatment continues:
- discontinuation of the drug until the target INR level is reached, if necessary, replace Warfarin with low molecular weight heparin;
- transfusion of prothrombin complex factor concentrates, fresh frozen plasma, or whole blood;
- the introduction of vitamin K in a dose of 5-10 mg by slow intravenous infusion, if necessary - repeated administration after 12 hours;
- therapy of developed complications.
Possible consequences
Overdose with Warfarin can have serious complications:
- acute myocardial infarction;
- hemorrhagic stroke;
- bleeding of various localization;
- fatal outcome.
Prevention
To prevent an overdose with Warfarin, it is necessary to carefully monitor the state of the blood coagulation system: regularly, at least once every 2 weeks, monitor the INR indicator and, if necessary, adjust the dose.
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Olesya Smolnyakova Therapy, clinical pharmacology and pharmacotherapy About the author
Education: higher, 2004 (GOU VPO "Kursk State Medical University"), specialty "General Medicine", qualification "Doctor". 2008-2012 - Postgraduate student of the Department of Clinical Pharmacology, KSMU, Candidate of Medical Sciences (2013, specialty "Pharmacology, Clinical Pharmacology"). 2014-2015 - professional retraining, specialty "Management in education", FSBEI HPE "KSU".
The information is generalized and provided for informational purposes only. At the first sign of illness, see your doctor. Self-medication is hazardous to health!
